1. The Field of the Invention
The present invention relates generally to catheter assemblies used to move fluid within an internal body site.
2. The Relevant Technology
Catheters are ubiquitous in many surgical and clinical procedures. Catheters are used to move fluids between an internal body site and a point outside the body. Catheters can be used to deliver fluids, including medications, or they can be used to evacuate fluids from a wound created by surgery, trauma, or disease. Typically, catheters are connected to a reservoir for either supplying or collecting the fluid moving between the internal body site and the extracorporeal site.
Catheters are commonly provided in the form of a tube having a central lumen bounded by a sidewall and one or more ports extending through the sidewall that communicate between the lumen and an exterior surface of the catheter. Other catheters known in the art simply use the terminus of the lumen at the distal end of the catheter as a port. Fluid is moved between the lumen and the internal body site through the ports by application of a pressure to the lumen. The applied pressure is less than the pressure at the internal body site when aspiration is desired, and the applied pressure is greater than the pressure at the internal body site when infusion is desired.
One example of the use of a catheter is the performance of surgical site infusion or aspiration. After the completion of a surgical procedure, a catheter is placed through the skin so that the ports of the catheter are located at or peripheral to the operative site. After the surgical incision or wound is closed, the catheter can be used to deliver medication, such as an antibiotic to treat infection or an analgesic to treat pain, to the internal body site. Alternatively, a catheter placed as just described can be used to evacuate blood and other fluid build-up at the internal body site in order to alleviate swelling and pain.
Catheters for infusion and aspiration known in the art do not reliably provide for a complete perfusion of fluid across the intended site of treatment. The portion of the catheter having the ports is surrounded by layers of tissue that collapse around and put pressure on the exterior surface of the catheter, thereby impeding the movement of fluid through some or all of the ports. During infusion or aspiration, the fluid that is forced into or out of the internal body site will preferentially travel along low resistance pathways, such as folds in the tissue layers, open spaces between tissue structures, or places where the tissue layers are held apart by the very catheter used to move the fluid. This means that, during infusion, fluids forced into the internal body site will travel and collect in low resistance pathways and will not flow into areas where tissue layers are compressed together. Similarly, during aspiration, the tendency of fluid to move along low resistance pathways as described will result in fluids trapped in pockets and sinuses that are isolated from other low resistance pathways that connect to the catheter. Thus, there is a need to provide a catheter that can more effectively move fluid across a target area, the target area being the area of body tissues that has suffered surgical insult, trauma, or disease.
Additionally, catheters commonly have multiple ports for fluid ingress and/or egress. However, the ports are typically of a common size and have a common spacing, resulting in different flow rates at each port as the pressure difference between the extracorporeal site and the internal body site decreases along the length of the catheter due to friction loss and pressure drops across ports. The result is a higher flow rate through proximal ports and lower flow rates through distal ports, providing an uneven rate of flow across the target site. Pressure drops between proximal and distal ports may be so great that distal ports have no flow at all. Therefore, a need exists for a catheter that can induce an even movement of fluid across the target area so that the target area is effectively treated.